System and methods for directional steering of electrical stimulation

ABSTRACT

Method and systems for determining a set of stimulation parameters for an implantable stimulation device include performing the following steps or actions: receiving a stimulation target; determining a target stimulation field based on the stimulation target; receiving a weighting for a plurality of spatial regions defined relative to a lead including a plurality of electrodes, where a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determining, using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 62/327,296, filed Apr. 25, 2016, which is incorporated herein by reference.

FIELD

The invention is directed to the area of electrical stimulation systems and leads and methods of making and using the systems and leads. The present invention is also directed to systems and methods for directional steering of electrical stimulation, as well as methods of making and using systems.

BACKGROUND

Electrical stimulation can be useful for treating a variety of conditions. Deep brain stimulation can be useful for treating, for example, Parkinson's disease, dystonia, essential tremor, chronic pain, Huntington's disease, levodopa-induced dyskinesias and rigidity, bradykinesia, epilepsy and seizures, eating disorders, and mood disorders. Typically, a lead with a stimulating electrode at or near a tip of the lead provides the stimulation to target neurons in the brain. Magnetic resonance imaging (“MM”) or computerized tomography (“CT”) scans can provide a starting point for determining where the stimulating electrode should be positioned to provide the desired stimulus to the target neurons.

After the lead is implanted into a patient's brain, electrical stimulus current can be delivered through selected electrodes on the lead to stimulate target neurons in the brain. The electrodes can be formed into rings or segments disposed on a distal portion of the lead. The stimulus current projects from the electrodes. Using segmented electrodes can provide directionality to the stimulus current and permit a clinician to steer the current to a desired direction and stimulation field.

BRIEF SUMMARY

One embodiment is a computer-implemented method for determining a set of stimulation parameters for an implantable stimulation device, the method including: receiving, by a computer processor, a stimulation target; determining, by the computer processor, a target stimulation field based on the stimulation target; receiving, by the computer processor, a weighting for a plurality of spatial regions defined relative to a lead including a plurality of electrodes, where a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determining, by the computer processor and using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.

Another embodiment is a non-transitory computer-readable medium having processor-executable instructions for determining a set of stimulation parameters, the processor-executable instructions when installed onto a device enable the device to perform actions, including: receive a stimulation target; determine a target stimulation field based on the stimulation target; receive a weighting for a plurality of spatial regions defined relative to a lead including a plurality of electrodes, where a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determine, using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.

Yet another embodiment is a system for determining a set of stimulation parameters, the system including: a display; and a computer processor coupled to the display and configured and arranged to perform the following actions: receive a stimulation target; determine a target stimulation field based on the stimulation target; receive a weighting for a plurality of spatial regions defined relative to a lead including a plurality of electrodes, where a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determine, using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field. In at least some embodiments, the system further includes an implantable lead and an implantable control module coupleable to the lead and configured and arranged to receive the set of stimulation parameters from the computer processor and to deliver electrical stimulation to a patient using the lead according to the set of stimulation parameters.

In at least some embodiments, the method or actions further include transmitting the set of stimulation parameters for reception by an implantable stimulation device for delivery of electrical stimulation to a patient. In at least some embodiments, a default weighting is assigned to each spatial region absent user selection of the weighting for that spatial region.

In at least some embodiments, the stimulation target is a center of stimulation or a virtual electrode. In at least some embodiments, receiving a stimulation target includes receiving a drawing of the virtual electrode on a representation of the lead.

In at least some embodiments, the steps or actions of receiving a stimulation target and determining a target stimulation field together include receiving a user-defined target stimulation field. In at least some embodiments, receiving a user-defined target stimulation field includes receiving a drawing of the user-defined target stimulation field relative to a representation of the lead.

In at least some embodiments, the method or actions further include receiving a user-definition of at least one of the spatial regions relative to a representation of the implanted lead. In at least some embodiments, determining, using the weightings for the plurality of spatial regions, a set of stimulation parameters includes minimizing a weighted error between the generated stimulation field and the target stimulation field using the weightings for the spatial regions. In at least some embodiments, the method or actions further include receiving a selection of a model for determining the weighted error. In at least some embodiments, the method or actions further include displaying the target stimulation field and the generated stimulation field.

In at least some embodiments, the method or actions further include receiving, by the computer processor, a setting of at least one of the electrodes to a zero stimulation amplitude prior to the determining of the set of stimulation parameters and requiring, during the determination of the set of stimulation parameters, that the at least one of the electrodes set to the zero stimulation amplitude remains at the zero stimulation amplitude. In at least some embodiments, the method or actions further include upon receiving the setting of the at least one of the electrodes to a zero amplitude, presenting a menu of user-selectable reasons for the setting.

In at least some embodiments, the method or actions further include receiving, by the computer processor, a setting of at least one of the electrodes to a fixed stimulation amplitude prior to the determining of the set of stimulation parameters and requiring, during the determination of the set of stimulation parameters, that the at least one of the electrodes set to the fixed stimulation amplitude remains at the fixed stimulation amplitude.

In at least some embodiments, the weighting for user selection is a qualitative, non-numerical description of the weighting. In at least some embodiments, the spatial regions are pre-defined. In at least some embodiments, the spatial regions include at least one close region, at least one medial region, and at least one far region, where the at least one close region is defined nearer the lead than the at least one medial region which, in turn, is defined nearer the lead than the at least one far region.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified.

For a better understanding of the present invention, reference will be made to the following Detailed Description, which is to be read in association with the accompanying drawings, wherein:

FIG. 1 is a schematic side view of one embodiment of a device for brain stimulation, according to the invention;

FIG. 2 is a schematic diagram of radial current steering along various electrode levels along the length of a lead, according to the invention;

FIG. 3A is a perspective view of an embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3B is a perspective view of a second embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3C is a perspective view of a third embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3D is a perspective view of a fourth embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3E is a perspective view of a fifth embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3F is a perspective view of a sixth embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3G is a perspective view of a seventh embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 3H is a perspective view of an eighth embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention;

FIG. 4 is a schematic flowchart of one embodiment of a method of determining a set of stimulation parameters, according to the invention;

FIG. 5A is a schematic illustration of one embodiment of an interface illustrating a distal end of a lead and a selected virtual electrode, according to the invention;

FIG. 5B is a schematic illustration of one embodiment of an interface illustrating a lateral cross-section of a distal end of a lead and a selected virtual electrode, according to the invention;

FIG. 6A is a schematic illustration of one embodiment of an interface illustrating multiple spatial regions (with a portion of the model of the lead obscured to better illustrate the spatial regions), according to the invention;

FIG. 6B is a schematic illustration of the interface of 6A with one example of a selection of weightings for the spatial regions, according to the invention;

FIG. 6C is a schematic illustration of the interface of 6A with another example of a selection of weightings for the spatial regions, according to the invention;

FIG. 7 is a schematic illustration of one model for determining a weighted error using a grid of points with a same number of points in each spatial region, according to the invention;

FIG. 8 is a schematic illustration of another model for determining a weighted error using a grid of points with a number of points in each spatial region depending on the weighting, according to the invention;

FIG. 9 is a schematic illustration of one embodiment of an interface illustrating setting of an electrode to a zero amplitude, according to the invention;

FIG. 10 is a schematic illustration of one embodiment of an interface illustrating setting of an electrode to a fixed amplitude, according to the invention; and

FIG. 11 is a schematic illustration of one embodiment of a system for practicing the invention.

DETAILED DESCRIPTION

The invention is directed to the area of electrical stimulation systems and leads and methods of making and using the systems and leads. The present invention is also directed to systems and methods for directional steering of electrical stimulation, as well as methods of making and using systems.

A lead for deep brain stimulation can include stimulation electrodes, recording electrodes, or a combination of both. At least some of the stimulation electrodes, recording electrodes, or both are provided in the form of segmented electrodes that extend only partially around the circumference of the lead. These segmented electrodes can be provided in sets of electrodes, with each set having electrodes radially distributed about the lead at a particular longitudinal position. For illustrative purposes, the leads are described herein relative to use for deep brain stimulation, but it will be understood that any of the leads can be used for applications other than deep brain stimulation, including spinal cord stimulation, peripheral nerve stimulation, or stimulation of other nerves and tissues.

Suitable implantable electrical stimulation systems include, but are not limited to, a least one lead with one or more electrodes disposed on a distal end of the lead and one or more terminals disposed on one or more proximal ends of the lead. Leads include, for example, percutaneous leads. Examples of electrical stimulation systems with leads are found in, for example, U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029; 6,609,032; 6,741,892; 7,244,150; 7,450,997; 7,672,734; 7,761,165; 7,783,359; 7,792,590; 7,809,446; 7,949,395; 7,974,706; 8,175,710; 8,224,450; 8,271,094; 8,295,944; 8,364,278; 8,391,985; and 8,688,235; and U.S. Patent Applications Publication Nos. 2007/0150036; 2009/0187222; 2009/0276021; 2010/0076535; 2010/0268298; 2011/0005069; 2011/0004267; 2011/0078900; 2011/0130817; 2011/0130818; 2011/0238129; 2011/0313500; 2012/0016378; 2012/0046710; 2012/0071949; 2012/0165911; 2012/0197375; 2012/0203316; 2012/0203320; 2012/0203321; 2012/0316615; 2013/0105071; and 2013/0197602, all of which are incorporated by reference.

In at least some embodiments, a practitioner may determine the position of the target neurons using recording electrode(s) and then position the stimulation electrode(s) accordingly. In some embodiments, the same electrodes can be used for both recording and stimulation. In some embodiments, separate leads can be used; one with recording electrodes which identify target neurons, and a second lead with stimulation electrodes that replaces the first after target neuron identification. In some embodiments, the same lead can include both recording electrodes and stimulation electrodes or electrodes can be used for both recording and stimulation.

FIG. 1 illustrates one embodiment of a device 100 for electrical stimulation (for example, brain or spinal cord stimulation). The device includes a lead 110, a plurality of electrodes 125 disposed at least partially about a circumference of the lead 110, a plurality of terminals 135, a connector 132 for connection of the electrodes to a control module, and a stylet 140 for assisting in insertion and positioning of the lead in the patient's brain. The stylet 140 can be made of a rigid material. Examples of suitable materials for the stylet include, but are not limited to, tungsten, stainless steel, and plastic. The stylet 140 may have a handle 150 to assist insertion into the lead 110, as well as rotation of the stylet 140 and lead 110. The connector 132 fits over a proximal end of the lead 110, preferably after removal of the stylet 140. The connector 132 can be part of a control module 133 or can be part of an optional lead extension 131 that is coupled to the control module.

The control module 133 can be an implantable pulse generator that can be implanted into a patient's body, for example, below the patient's clavicle area. The control module can have eight stimulation channels which may be independently programmable to control the magnitude of the current stimulus from each channel. In some cases the control module can have more or fewer than eight stimulation channels (e.g., 4-, 6-, 16-, 32-, or more stimulation channels). The control module can have one, two, three, four, or more connector ports, for receiving the plurality of terminals 135 at the proximal end of the lead 110. Examples of control modules are described in the references cited above.

In one example of operation, access to the desired position in the brain can be accomplished by drilling a hole in the patient's skull or cranium with a cranial drill (commonly referred to as a burr), and coagulating and incising the dura mater, or brain covering. The lead 110 can be inserted into the cranium and brain tissue with the assistance of the stylet 140. The lead 110 can be guided to the target location within the brain using, for example, a stereotactic frame and a microdrive motor system. In some embodiments, the microdrive motor system can be fully or partially automatic. The microdrive motor system may be configured to perform one or more the following actions (alone or in combination): insert the lead 110, retract the lead 110, or rotate the lead 110.

In some embodiments, measurement devices coupled to the muscles or other tissues stimulated by the target neurons, or a unit responsive to the patient or clinician, can be coupled to the control module or microdrive motor system. The measurement device, user, or clinician can indicate a response by the target muscles or other tissues to the stimulation or recording electrode(s) to further identify the target neurons and facilitate positioning of the stimulation electrode(s). For example, if the target neurons are directed to a muscle experiencing tremors, a measurement device can be used to observe the muscle and indicate changes in tremor frequency or amplitude in response to stimulation of neurons. Alternatively, the patient or clinician can observe the muscle and provide feedback.

The lead 110 for deep brain stimulation can include stimulation electrodes, recording electrodes, or both. In at least some embodiments, the lead 110 is rotatable so that the stimulation electrodes can be aligned with the target neurons after the neurons have been located using the recording electrodes.

Stimulation electrodes may be disposed on the circumference of the lead 110 to stimulate the target neurons. Stimulation electrodes may be ring-shaped so that current projects from each electrode equally in every direction from the position of the electrode along a length of the lead 110. Ring electrodes typically do not enable stimulus current to be directed from only a limited angular range around of the lead. Segmented electrodes, however, can be used to direct stimulation energy to a selected angular range around the lead. When segmented electrodes are used in conjunction with an implantable control module that delivers constant current stimulus, current steering can be achieved to more precisely deliver the stimulus to a position around an axis of the lead (i.e., radial positioning around the axis of the lead).

To achieve current steering, segmented electrodes can be utilized in addition to, or as an alternative to, ring electrodes. Though the following description discusses stimulation electrodes, it will be understood that all configurations of the stimulation electrodes discussed may be utilized in arranging recording electrodes as well. A lead that includes segmented electrodes can be referred to as a directional lead because the segmented electrodes can be used to direct stimulation along a particular direction or range of directions.

The lead 100 includes a lead body 110, one or more optional ring electrodes 120, and a plurality of sets of segmented electrodes 130. The lead body 110 can be formed of a biocompatible, non-conducting material such as, for example, a polymeric material. Suitable polymeric materials include, but are not limited to, silicone, polyurethane, polyurea, polyurethane-urea, polyethylene, or the like. Once implanted in the body, the lead 100 may be in contact with body tissue for extended periods of time. In at least some embodiments, the lead 100 has a cross-sectional diameter of no more than 1.5 mm and may be in the range of 0.5 to 1.5 mm. In at least some embodiments, the lead 100 has a length of at least 10 cm and the length of the lead 100 may be in the range of 10 to 70 cm.

The electrodes can be made using a metal, alloy, conductive oxide, or any other suitable conductive biocompatible material. Examples of suitable materials include, but are not limited to, platinum, platinum iridium alloy, iridium, titanium, tungsten, palladium, palladium rhodium, or the like. Preferably, the electrodes are made of a material that is biocompatible and does not substantially corrode under expected operating conditions in the operating environment for the expected duration of use.

Each of the electrodes can either be used or unused (OFF). When the electrode is used, the electrode can be used as an anode or cathode and carry anodic or cathodic current. In some instances, an electrode might be an anode for a period of time and a cathode for a period of time.

Stimulation electrodes in the form of ring electrodes 120 can be disposed on any part of the lead body 110, usually near a distal end of the lead 100. In FIG. 1, the lead 100 includes two ring electrodes 120. Any number of ring electrodes 120 can be disposed along the length of the lead body 110 including, for example, one, two three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen or more ring electrodes 120. It will be understood that any number of ring electrodes can be disposed along the length of the lead body 110. In some embodiments, the ring electrodes 120 are substantially cylindrical and wrap around the entire circumference of the lead body 110. In some embodiments, the outer diameters of the ring electrodes 120 are substantially equal to the outer diameter of the lead body 110. The length of the ring electrodes 120 may vary according to the desired treatment and the location of the target neurons. In some embodiments the length of the ring electrodes 120 are less than or equal to the diameters of the ring electrodes 120. In other embodiments, the lengths of the ring electrodes 120 are greater than the diameters of the ring electrodes 120. The distal-most ring electrode 120 may be a tip electrode (see, e.g., tip electrode 320 a of FIG. 3E) which covers most, or all, of the distal tip of the lead.

Deep brain stimulation leads may include one or more sets of segmented electrodes. Segmented electrodes may provide for superior current steering than ring electrodes because target structures in deep brain stimulation are not typically symmetric about the axis of the distal electrode array. Instead, a target may be located on one side of a plane running through the axis of the lead. Through the use of a radially segmented electrode array (“RSEA”), current steering can be performed not only along a length of the lead but also around a circumference of the lead. This provides precise three-dimensional targeting and delivery of the current stimulus to neural target tissue, while potentially avoiding stimulation of other tissue. Examples of leads with segmented electrodes include U.S. Patent Applications Publication Nos. 2010/0268298; 2011/0005069; 2011/0078900; 2011/0130803; 2011/0130816; 2011/0130817; 2011/0130818; 2011/0078900; 2011/0238129; 2011/0313500; 2012/0016378; 2012/0046710; 2012/0071949; 2012/0165911; 2012/197375; 2012/0203316; 2012/0203320; 2012/0203321; 2013/0197602; 2013/0261684; 2013/0325091; 2013/0317587; 2014/0039587; 2014/0353001; 2014/0358209; 2014/0358210; 2015/0018915; 2015/0021817; 2015/0045864; 2015/0021817; 2015/0066120; 2013/0197424; 2015/0151113; 2014/0358207; and U.S. Pat. No. 8,483,237, all of which are incorporated herein by reference in their entireties. Examples of leads with tip electrodes include at least some of the previously cited references, as well as U.S. Patent Applications Publication Nos. 2014/0296953 and 2014/0343647, all of which are incorporated herein by reference in their entireties.

The lead 100 is shown having a plurality of segmented electrodes 130. Any number of segmented electrodes 130 may be disposed on the lead body 110 including, for example, one, two three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen or more segmented electrodes 130. It will be understood that any number of segmented electrodes 130 may be disposed along the length of the lead body 110. A segmented electrode 130 typically extends only 75%, 67%, 60%, 50%, 40%, 33%, 25%, 20%, 17%, 15%, or less around the circumference of the lead.

The segmented electrodes 130 may be grouped into sets of segmented electrodes, where each set is disposed around a circumference of the lead 100 at a particular longitudinal portion of the lead 100. The lead 100 may have any number segmented electrodes 130 in a given set of segmented electrodes. The lead 100 may have one, two, three, four, five, six, seven, eight, or more segmented electrodes 130 in a given set. In at least some embodiments, each set of segmented electrodes 130 of the lead 100 contains the same number of segmented electrodes 130. The segmented electrodes 130 disposed on the lead 100 may include a different number of electrodes than at least one other set of segmented electrodes 130 disposed on the lead 100.

The segmented electrodes 130 may vary in size and shape. In some embodiments, the segmented electrodes 130 are all of the same size, shape, diameter, width or area or any combination thereof. In some embodiments, the segmented electrodes 130 of each circumferential set (or even all segmented electrodes disposed on the lead 100) may be identical in size and shape.

Each set of segmented electrodes 130 may be disposed around the circumference of the lead body 110 to form a substantially cylindrical shape around the lead body 110. The spacing between individual electrodes of a given set of the segmented electrodes may be the same, or different from, the spacing between individual electrodes of another set of segmented electrodes on the lead 100. In at least some embodiments, equal spaces, gaps or cutouts are disposed between each segmented electrode 130 around the circumference of the lead body 110. In other embodiments, the spaces, gaps or cutouts between the segmented electrodes 130 may differ in size or shape. In other embodiments, the spaces, gaps, or cutouts between segmented electrodes 130 may be uniform for a particular set of the segmented electrodes 130, or for all sets of the segmented electrodes 130. The sets of segmented electrodes 130 may be positioned in irregular or regular intervals along a length the lead body 110.

Conductor wires that attach to the ring electrodes 120 or segmented electrodes 130 extend along the lead body 110. These conductor wires may extend through the material of the lead 100 or along one or more lumens defined by the lead 100, or both. The conductor wires couple the electrodes 120, 130 to the terminals 135.

When the lead 100 includes both ring electrodes 120 and segmented electrodes 130, the ring electrodes 120 and the segmented electrodes 130 may be arranged in any suitable configuration. For example, when the lead 100 includes two ring electrodes 120 and two sets of segmented electrodes 130, the ring electrodes 120 can flank the two sets of segmented electrodes 130 (see e.g., FIGS. 1, 3A, and 3E-3H—ring electrodes 320 and segmented electrode 330). Alternately, the two sets of ring electrodes 120 can be disposed proximal to the two sets of segmented electrodes 130 (see e.g., FIG. 3C—ring electrodes 320 and segmented electrode 330), or the two sets of ring electrodes 120 can be disposed distal to the two sets of segmented electrodes 130 (see e.g., FIG. 3D—ring electrodes 320 and segmented electrode 330). One of the ring electrodes can be a tip electrode (see, tip electrode 320 a of FIGS. 3E and 3G). It will be understood that other configurations are possible as well (e.g., alternating ring and segmented electrodes, or the like).

By varying the location of the segmented electrodes 130, different coverage of the target neurons may be selected. For example, the electrode arrangement of FIG. 3C may be useful if the physician anticipates that the neural target will be closer to a distal tip of the lead body 110, while the electrode arrangement of FIG. 3D may be useful if the physician anticipates that the neural target will be closer to a proximal end of the lead body 110.

Any combination of ring electrodes 120 and segmented electrodes 130 may be disposed on the lead 100. For example, the lead may include a first ring electrode 120, two sets of segmented electrodes; each set formed of four segmented electrodes 130, and a final ring electrode 120 at the end of the lead. This configuration may simply be referred to as a 1-4-4-1 configuration (FIGS. 3A and 3E—ring electrodes 320 and segmented electrode 330). It may be useful to refer to the electrodes with this shorthand notation. Thus, the embodiment of FIG. 3C may be referred to as a 1-1-4-4 configuration, while the embodiment of FIG. 3D may be referred to as a 4-4-1-1 configuration. The embodiments of FIGS. 3F, 3G, and 3H can be referred to as a 1-3-3-1 configuration. Other electrode configurations include, for example, a 2-2-2-2 configuration, where four sets of segmented electrodes are disposed on the lead, and a 4-4 configuration, where two sets of segmented electrodes, each having four segmented electrodes 130 are disposed on the lead. The 1-3-3-1 electrode configuration of FIGS. 3F, 3G, and 3H has two sets of segmented electrodes, each set containing three electrodes disposed around the circumference of the lead, flanked by two ring electrodes (FIGS. 3F and 3H) or a ring electrode and a tip electrode (FIG. 3G). In some embodiments, the lead includes 16 electrodes. Possible configurations for a 16-electrode lead include, but are not limited to 4-4-4-4; 8-8; 3-3-3-3-3-1 (and all rearrangements of this configuration); and 2-2-2-2-2-2-2-2.

FIG. 2 is a schematic diagram to illustrate radial current steering along various electrode levels along the length of the lead 200. While conventional lead configurations with ring electrodes are only able to steer current along the length of the lead (the z-axis), the segmented electrode configuration is capable of steering current in the x-axis, y-axis as well as the z-axis. Thus, the centroid of stimulation may be steered in any direction in the three-dimensional space surrounding the lead 200. In some embodiments, the radial distance, r, and the angle θ around the circumference of the lead 200 may be dictated by the percentage of anodic current (recognizing that stimulation predominantly occurs near the cathode, although strong anodes may cause stimulation as well) introduced to each electrode. In at least some embodiments, the configuration of anodes and cathodes along the segmented electrodes allows the centroid of stimulation to be shifted to a variety of different locations along the lead 200.

As can be appreciated from FIG. 2, the centroid of stimulation can be shifted at each level along the length of the lead 200. The use of multiple sets of segmented electrodes at different levels along the length of the lead allows for three-dimensional current steering. In some embodiments, the sets of segmented electrodes are shifted collectively (i.e., the centroid of simulation is similar at each level along the length of the lead). In at least some other embodiments, each set of segmented electrodes is controlled independently. Each set of segmented electrodes may contain two, three, four, five, six, seven, eight or more segmented electrodes. It will be understood that different stimulation profiles may be produced by varying the number of segmented electrodes at each level. For example, when each set of segmented electrodes includes only two segmented electrodes, uniformly distributed gaps (inability to stimulate selectively) may be formed in the stimulation profile. In some embodiments, at least three segmented electrodes 230 in a set are utilized to allow for true 360° selectivity.

As previously indicated, the foregoing configurations may also be used while utilizing recording electrodes. In some embodiments, measurement devices coupled to the muscles or other tissues stimulated by the target neurons or a unit responsive to the patient or clinician can be coupled to the control module or microdrive motor system. The measurement device, user, or clinician can indicate a response by the target muscles or other tissues to the stimulation or recording electrodes to further identify the target neurons and facilitate positioning of the stimulation electrodes. For example, if the target neurons are directed to a muscle experiencing tremors, a measurement device can be used to observe the muscle and indicate changes in tremor frequency or amplitude in response to stimulation of neurons. Alternatively, the patient or clinician may observe the muscle and provide feedback.

The reliability and durability of the lead will depend heavily on the design and method of manufacture. Fabrication techniques discussed below provide methods that can produce manufacturable and reliable leads.

Returning to FIG. 1, when the lead 100 includes a plurality of sets of segmented electrodes 130, it may be desirable to form the lead 100 such that corresponding electrodes of different sets of segmented electrodes 130 are radially aligned with one another along the length of the lead 100 (see e.g., the segmented electrodes 130 shown in FIG. 1). Radial alignment between corresponding electrodes of different sets of segmented electrodes 130 along the length of the lead 100 may reduce uncertainty as to the location or orientation between corresponding segmented electrodes of different sets of segmented electrodes. Accordingly, it may be beneficial to form electrode arrays such that corresponding electrodes of different sets of segmented electrodes along the length of the lead 100 are radially aligned with one another and do not radially shift in relation to one another during manufacturing of the lead 100.

In other embodiments, individual electrodes in the two sets of segmented electrodes 130 are staggered (see, FIG. 3B) relative to one another along the length of the lead body 110. In some cases, the staggered positioning of corresponding electrodes of different sets of segmented electrodes along the length of the lead 100 may be designed for a specific application.

Segmented electrodes can be used to tailor the stimulation region so that, instead of stimulating tissue around the circumference of the lead as would be achieved using a ring electrode, the stimulation region can be directionally targeted. In some instances, it is desirable to target a parallelepiped (or slab) region 250 that contains the electrodes of the lead 200, as illustrated in FIG. 2. One arrangement for directing a stimulation field into a parallelepiped region uses segmented electrodes disposed on opposite sides of a lead.

FIGS. 3A-3H illustrate leads 300 with segmented electrodes 330, optional ring electrodes 320 or tip electrodes 320 a, and a lead body 310. The sets of segmented electrodes 330 each include either two (FIG. 3B), three (FIGS. 3E-3H), or four (FIGS. 3A, 3C, and 3D) or any other number of segmented electrodes including, for example, three, five, six, or more. The sets of segmented electrodes 330 can be aligned with each other (FIGS. 3A-3G) or staggered (FIG. 3H)

Any other suitable arrangements of segmented electrodes can be used. As an example, arrangements in which segmented electrodes are arranged helically with respect to each other. One embodiment includes a double helix.

In at least some instances, a treating physician may wish to tailor the stimulation parameters (such as which one or more of the stimulating electrode contacts to use, the stimulation pulse amplitude (such as current or voltage amplitude depending on the stimulator being used) the stimulation pulse width, the stimulation frequency, or the like or any combination thereof) for a particular patient to improve the effectiveness of the therapy. Electrical stimulation systems can provide an interface that facilitates parameter selections. Examples of such systems and interfaces can be found in, for example, U.S. patent application Ser. Nos. 12/454,330; 12/454,312; 12/454,340; 12/454,3431; and 12/454,314 and U.S. Patent Application Publication No. 2014/0277284, all of which are incorporated herein by reference in their entireties.

Conventional electrical stimulation (such as deep brain or spinal cord stimulation) can include a programming procedure that is often performed in an initial session and, in at least some instances, at later sessions. The procedure can involve, for example, testing different sets of stimulation parameters (which can include variations in the electrodes that are selected as well as different electrical parameters such as amplitude, duration, pulse frequency, and the like) and annotating when there is a beneficial therapeutic effect or an unwanted side effect. In at least some embodiments, the clinician performs a monopolar review testing each electrode individually and recording therapeutic/beneficial effects and side effects for each electrode on the lead corresponding to different values of the stimulation amplitude or other stimulation parameters. The clinician may also perform bipolar or multipolar reviews using two or more electrodes.

In contrast to these conventional methods, automated steering algorithms and systems can enable or enhance stimulation field shaping to generate customized, user-defined targets rather than relying on manual programming or limiting users to pre-set configurations. Such algorithms and systems may provide greater ease of use and flexibility and may enable or enhance specific targeting of stimulation therapy. The terms “stimulation field map” (SFM) and “volume of activation” (VOA) are often used to designate an estimated region of tissue that will be stimulated for a particular set of stimulation parameters.

As described herein, a clinician or other individual can specify a desired virtual electrode or stimulation target. An automated system can identify stimulation parameters for the actual electrodes on the lead that attempt to fit this virtual electrode or stimulation target. In many instances, the fit is not exact and, therefore, it is useful to provide instructions regarding finding a best or desirable fit. The systems and methods described herein take into account user-selected weighting of regions around the lead. In many instances, the field near the electrodes is more important than the field further from the electrodes. Accordingly, a user can weight the regions around the lead based on importance of that region to the overall stimulation. In at least some embodiments, the user may also exclude one or more of the electrodes of the lead in the determination of stimulation parameters or set one or more of the electrodes at a desired amplitude.

FIG. 4 presents in a flowchart one embodiment of a method of determining stimulation parameters for an electrical stimulation program. In the description below, the amplitude and polarity of the stimulation at one or more of the electrodes are determined using the method, but it will be understood that other parameters, such as pulse width or pulse duration, may also be varied for individual electrodes or one or more groups of electrodes. For example, the lead can be any of the leads illustrated in the Figures or any other suitable lead with multiple electrodes in any suitable arrangement. Also, although the electrodes are indicated as disposed on a single lead, it will be understood that electrodes from multiple leads can be used. Furthermore, it at least some embodiments, one or more electrodes may be provided on the housing of the control module. For example, the housing may have an electrode which acts as a cathode or anode.

In step 402, the user determines a target. The target can be, for example, a virtual electrode, a center of stimulation, or a target stimulation field. In at least some embodiments, a user interface can be provided with a representation of, for example, the distal portion of the lead and the available electrodes on that portion (or any other suitable representation of the lead or portion of the lead or portion of the anatomy in which the lead is implanted or to be implanted). The user interface may permit the user to select, draw, or otherwise indicate a center of stimulation, virtual electrode, or target stimulation field.

A “virtual electrode” is an electrode that is designated by the user which may or may not correspond to an actual electrode on the lead. FIG. 5A illustrates user interface with one example of a representation of a set of lead electrodes with a ring electrode 520 and a tip electrode 520 a separated by two sets with three segmented electrodes 530 each (i.e., the arrangement illustrated in FIG. 3G). In the illustrated embodiment, the user has selected or drawn a virtual electrode 535 that extends between and overlaps the two sets of segmented electrodes 530 and extends between and overlaps two segmented electrodes in each set. FIG. 5B illustrates another user interface with an example of a representation of three segmented electrodes 530 in a lateral cross-section with a virtual electrode 535 selected or drawn relative to the segmented electrodes. It will be understood that other methods or arrangement for selecting, drawing, or otherwise indicating a center of stimulation, virtual electrode, or target stimulation field can be used.

If a center of stimulation or virtual electrode or the like is selected, the system determines a target stimulation field based on that selection. The target stimulation field can be determined using any suitable method including, for example, estimating a field generated from the virtual electrode or from an electrode disposed at a point of the lead nearest the selected center of stimulation. In other embodiments, a stimulation field model (SFM) or volume of activation (VOA) can be used to determine the target stimulation field. Any suitable method for determining the SFM or VOA can be used including those described in, for example, U.S. Pat. Nos. 8,326,433; 8,675,945; 8,831,731; 8,849,632; and 8,958,615; U.S. Patent Application Publications Nos. 2009/0287272; 2009/0287273; 2012/0314924; 2013/0116744; 2014/0122379; and 2015/0066111; and U.S. Provisional Patent Application Ser. No. 62/030,655, all of which are incorporated herein by reference in their entirety.

In optional step 404, parameters of one or more of the electrodes can be set. For example, one or more of the electrodes may be set to zero amplitude or to a fixed amplitude. Additionally or alternatively, parameters such as pulse width or maximum amplitude or total amplitude may be set. In at least some embodiments, one or more of these parameters may be predefined.

In step 406, the relative weights for one or more spatial regions around the lead is selected. The objective of the procedure is to determine stimulation parameters for the existing electrodes that will approximately generate the target stimulation field. The stimulation field generated by the stimulation parameters will not be exactly the same as the target stimulation field, so at least some conventional systems select stimulation parameters that minimize the difference between the generated stimulation field and the target stimulation field. In contrast, the present methods and systems recognize that deviation from the target stimulation field in some spatial regions may be more significant than the same deviation in other areas. For example, in some instances, conformance of the generated stimulation field to the target stimulation field near the lead is more important that conformance far away from the lead. The present methods and systems permit the user to modify the weighting of the deviations from the target stimulation field for different spatial regions around the lead. In at least some embodiments, the user may also be allowed to define spatial regions around the lead and then select weighting for those spatial regions. In at least some embodiments, the spatial regions can be predefined. In at least some embodiments, the weights of the different regions may be predefined or predetermined. Optionally, these predefined or predetermined weights may be modifiable by the user.

FIG. 6A illustrates one embodiment of a user interface 650 with a representation 600 of the lead or electrodes and six regions 640 labeled “1” through “6”. (For clarity of illustration, the portion of the representation 600 in regions “1” and “2” has been deleted so that those regions can be clearly identified. Compare with FIG. 7.) In this embodiment, regions “1” and “2” are near the lead, regions “3” and “4” are at medium distance from the lead, and regions “5” and “6” are at a far distance from the lead. The user interface 650 also includes a selection area 652 for selecting the weighting for the regions 640.

FIG. 6B illustrates the user interface 650 with a “High” weighting selected for regions “1” and “2”, a “Medium” weighting selected for regions “3” and “4”, and a “Low” weighting selected for regions “5” and “6”. FIG. 6B also illustrates a selected center of stimulation 642 and a region of expected stimulation 644 based on that center of stimulation. In addition, the regions 650 have been graphically modified based on the selected weighting. Such graphical modifications can be, for example, differences in color, shading, cross-hatching, or any other suitable visible indicator. This graphical modification of the regions is optional, but can be helpful for visualization of the weighting.

FIG. 6C illustrates another user interface 650 with a “High” weighting selected for region “3”, a “Medium” weighting selected for regions “1”, “2”, and “4”, and a “Low” weighting selected for regions “5” and “6”. FIG. 6C also illustrates a region of expected stimulation 644.

The illustrated embodiments use three categories of weighting: “High”, “Medium”, and “Low”. This categorization is a non-numerical qualitative description of the weighting. Other types of categorization can be used including, but not limited to, numerical categorization or qualitative numerical descriptions (where the numbers are not necessarily indicative of the weighting value, but rather are intended to convey a relative importance of the region.) In some embodiments, the user may enter a weighting, select a weighting from a menu or other list, or use a scale or slider to select a weighting. The scale or slider may be a numeric or non-numeric scale or slider. In some embodiments, the weight can also be selected to be zero or “None” or the like. In some embodiments, a weight or designation can also be selected to indicate that the region is to be avoided (for example, that the generated stimulation field should avoid or minimize extension into that regions.)

The illustrated embodiment utilizes three categories, but it will be recognized that more or fewer weighting categories can also be used including, but not limited to, two, three, four, five, six, eight, ten, or twelve or more categories. In at least some embodiments, each weighting category can be associated with a numerical value, w_(i), where i is an integer representing the category. For example, “High” can have a numerical value of 5, “Medium” can have a numerical value of 3, and “Low” can have a numerical value of 1.

In the illustrated embodiments, the generated stimulation field based on the stimulation parameters that will be determined will be more precise and refined, relative to the target stimulation field, in regions with “High” weighting. In regions with “Low” weighting, conformance of the generated stimulation field with the target stimulation field will be lower and assigning regions to “Low” may also improve calculation speed and efficiency.

In optional step 408, the user may be permitted to select from two or more different weighting models. In other embodiments, one of the models may be automatically used or the system or method can employ multiple models and combine the results or present several results for selection or use by the user or system.

One example of a weighting model uses a uniform grid of points 660 arranged over the regions 640, as illustrated in FIG. 7. The stimulation field potential (φ_(actual)) at each point is determined based on a set of stimulation parameters and then compared to the target stimulation field potential (φ_(target)) at that point. The stimulation field potential can be described by the equation: ĵ=A⁻¹φ_(actual) where ĵ is a set of electrode amplitudes or relative weightings (i.e., the set of electrodes selected to produce the target stimulation field potential) and A are the extracellular potentials generated by unit amplitudes. An error (ε) is defined as ε=|Aĵ−φ_(target)|. The error will depend on the number of points within each region. In at least some embodiments, each region will be assigned the same number of points, as illustrated in FIG. 7. The error term arising from each region, however, will be weighted differently according to the selected weights which means that the contribution of a region to the overall error can be enhanced or reduced by selection of the weight.

This inverse modeling technique then seeks to minimize or reduce the error between potentials at all points generated by the actual electrodes (φ_(actual)) and the target stimulation field potential (φ_(target)). As an example, one embodiment has two regions: near field (nf) and far field (ff). Associated with these fields are a near field weight (w_(nf)) and a far field weight (w_(ff)). The error (ε) has a weighted near field component (w_(nf)·ε) and a far field component (w_(ff)·ε) where

ε=|Aĵ−φ _(target)|

w _(nf) ·ε=w _(nf) ·|A _(nf) ĵ−φ _(target,nf)|

w _(ff) ·=w _(ff) ·|A _(ff) ĵ−φ _(target,ff)|.

If the number of near region and far region observational points are the same, using the subadditivity property of absolute values |a+b|≦|a|+|b| and assuming the “worst case” where |a+b| equal to |a|+|b|) then:

ε_(total) =w _(nf)·ε_(nf) +w _(ff)·ε_(ff) =|w _(nf) ·A _(nf) ĵ−w _(nf)·φ_(target,nf) +w _(ff) ·A _(ff) ĵ−w _(ff)·φ_(target,ff)|

ε_(total) =w _(nf)·ε_(nf) +w _(ff)·ε_(ff)=|(w _(nf) ·A _(nf) +w _(ff) ·A _(ff)){circumflex over (j)}−(w _(nf)·φ_(target,nf) +w _(ff)·φ_(target,ff))|

The total error is then minimized or reduced by solving for ĵ such that

(w _(nf) ·A _(nf) +w _(ff) ·A _(ff)){circumflex over (j)}=(w _(nf)·φ_(target,nf) +w _(ff)·φ_(target,ff))

In an alternative model, instead of using the same number of points in each region, the weighting is accomplished by changing the relative number of points in each region, as illustrated in FIG. 8. In the illustrated embodiment, regions “1” and “2” (see, FIG. 6A) have the same number of points, regions “3” and “4” have only two thirds of the points of regions “1” and “2”, and regions “5” and “6” have only one third the points of regions “1” and “2”. In this model, the error value is simply the sum of differences between the actual stimulation field and target stimulation field at each point. The weighting in this model is accounted for by the difference in number of points for each region. In this model, regions with more points will produce more contributions to the error term and, therefore, minimizing or reducing the error term will result in closer adherence of the generated stimulation field to the target stimulation field in the regions with more points. This model may be more computationally efficient, but will have lower spatial resolution than the preceding model.

In at least some embodiments, the user interface can allow the user to define resolution of point(s) (e.g., the number of points in each region or in the highest weight regions) according to consideration of efficiency or computational time. In at least some embodiments, the user interface may allow the user to toggle between highest resolution (first model) and “efficiency” (second model) modes. These models are generalizable to all electrode geometries, any number of regions, and any selection of weights for those regions. It will also be recognized that any other suitable model that incorporates the selected weights for the regions can be used. It will also be recognized that each model may also incorporate one or more constraints on the model, such as, for example, the maximum amplitude for each electrode, the total maximum anodic or cathodic amplitude over all electrodes, the presence or amplitude for an electrode on the housing of the control module, or the like or any combination thereof.

In step 410, electrode parameters, such which electrodes are to be used, electrode polarity (e.g., anode or cathode), electrode amplitude, or the like or any combination thereof, are determined using a weighting model, such as one of the models described above. In step 412, the determined set of stimulation parameters are output to the user. In some embodiments, these parameters may be output to (for example, transmitted or otherwise conveyed to) the control module for delivery of stimulation to the patient based on these parameters. In some embodiments, the user interface may display the parameters. In some embodiments, the user interface may display the generated stimulation field that is estimated to be obtained using these parameters. The user interface may also display the target stimulation field and may optionally identify differences between the generated stimulation field and the target stimulation field. The user may also display the target stimulation field in relation to a model of the distal end of the lead and the electrodes of the lead, similar to the interface illustrated, for example, in FIGS. 6A-6C.

As described above, there may be situations when it is desirable that one or more of the electrodes are set to an off position or have a fixed amplitude. In one embodiment of a user interface 950, an electrode 930 can be selected and excluded using a control on the user interface, as illustrated in FIG. 9. In some embodiments, a side-menu 972 may be displayed asking the user to indicate a reason for excluding the electrode. Examples of reasons can include, but are not limited to, the electrode being a sensing electrode only, a diagnostic fault, a desire to avoid stimulation near that electrode, or a desire to discount or avoid consideration of a region near the electrode. The procedure illustrated in FIG. 4 can proceed with the excluded electrode set to 0. In some embodiments, the system may also disallow certain conditions. For example, the system may not allow specification of more sensing electrodes than there are sensor inputs in the device. The system may also warn or disallow drawing of a virtual electrode whose domain is only within the excluded electrode(s). In some embodiments, instead of setting a particular electrode to zero amplitude, the weighting of a region adjacent the electrode can be set to zero.

In at least some embodiments, an electrode 1030 a, 1030 b can be selected and fixed at a value using a control on the user interface 1050, as illustrated in FIG. 10. Values at which electrodes are fixed may be system-specified or entered by the user. The procedure illustrated in FIG. 4 can proceed with the selected electrode set to the fixed value. In at least some embodiments, a warning or error may be indicated by the system in the event of certain occurrences (for example, a virtual electrode falling fully within fixed electrodes, amplitudes exceeding tolerances, previously excluded electrode being fixed at nonzero value.

FIG. 11 illustrates one embodiment of a system for practicing the invention. The system can include a computer 1100 or any other similar device that includes a processor 1102 and a memory 1104, a display 1106, an input device 1108, and, optionally, the electrical stimulation system 1112.

The computer 1100 can be a laptop computer, desktop computer, tablet, mobile device, smartphone or other devices that can run applications or programs, or any other suitable device for processing information and for presenting a user interface (such as the user interfaces of FIGS. 5A, 5B, 6A-6C, 9, and 10). The computer can be, for example, a clinician or remote programmer for the electrical stimulation system 1112. The computer 1100 can be local to the user or can include components that are non-local to the computer including one or both of the processor 1102 or memory 1104 (or portions thereof). For example, in some embodiments, the user may operate a terminal that is connected to a non-local computer. In other embodiments, the memory can be non-local to the user.

The computer 1100 can utilize any suitable processor 1102 including one or more hardware processors that may be local to the user or non-local to the user or other components of the computer. The processor 1102 is configured to execute instructions provided to the processor, as described below.

Any suitable memory 1104 can be used for the computer 1102. The memory 1104 illustrates a type of computer-readable media, namely computer-readable storage media. Computer-readable storage media may include, but is not limited to, nonvolatile, non-transitory, removable, and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer-readable storage media include RAM, ROM, EEPROM, flash memory, or other memory technology, CD-ROM, digital versatile disks (“DVD”) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer.

Communication methods provide another type of computer readable media; namely communication media. Communication media typically embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, data signal, or other transport mechanism and include any information delivery media. The terms “modulated data signal,” and “carrier-wave signal” includes a signal that has one or more of its characteristics set or changed in such a manner as to encode information, instructions, data, and the like, in the signal. By way of example, communication media includes wired media such as twisted pair, coaxial cable, fiber optics, wave guides, and other wired media and wireless media such as acoustic, RF, infrared, and other wireless media.

The display 1106 can be any suitable display device, such as a monitor, screen, display, or the like, and can include a printer. The input device 1108 can be, for example, a keyboard, mouse, touch screen, track ball, joystick, voice recognition system, or any combination thereof, or the like and can be used by the user to interact with a user interface or clinical effects map.

The electrical stimulation system 1112 can include, for example, a control module 1114 (for example, an implantable pulse generator) and a lead 1116 (for example, the lead illustrated in FIG. 1.) The electrical stimulation system 1112 may communicate with the computer 1100 through a wired or wireless connection or, alternatively or additionally, a user can provide information between the electrical stimulation system 1112 and the computer 1100 using a computer-readable medium or by some other mechanism. In some embodiments, the computer 1100 may include part of the electrical stimulation system.

The methods and systems described herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Accordingly, the methods and systems described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Systems referenced herein typically include memory and typically include methods for communication with other devices including mobile devices. Methods of communication can include both wired and wireless (e.g., RF, optical, or infrared) communications methods and such methods provide another type of computer readable media; namely communication media. Wired communication can include communication over a twisted pair, coaxial cable, fiber optics, wave guides, or the like, or any combination thereof. Wireless communication can include RF, infrared, acoustic, near field communication, Bluetooth™, or the like, or any combination thereof.

It will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations and methods disclosed herein, can be implemented by computer program instructions. These program instructions may be provided to a processor to produce a machine, such that the instructions, which execute on the processor, create means for implementing the actions specified in the flowchart block or blocks disclosed herein. The computer program instructions may be executed by a processor to cause a series of operational steps to be performed by the processor to produce a computer implemented process. The computer program instructions may also cause at least some of the operational steps to be performed in parallel. Moreover, some of the steps may also be performed across more than one processor, such as might arise in a multi-processor computer system. In addition, one or more processes may also be performed concurrently with other processes, or even in a different sequence than illustrated without departing from the scope or spirit of the invention.

The computer program instructions can be stored on any suitable computer-readable medium including, but not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (“DVD”) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer.

The above specification, examples, and data provide a description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention also resides in the claims hereinafter appended. 

What is claimed as new and desired to be protected by Letters Patent of the United States is:
 1. A computer-implemented method for determining a set of stimulation parameters for an implantable stimulation device, the method comprising: receiving, by a computer processor, a stimulation target; determining, by the computer processor, a target stimulation field based on the stimulation target; receiving, by the computer processor, a weighting for a plurality of spatial regions defined relative to a lead comprising a plurality of electrodes, wherein a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determining, by the computer processor and using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.
 2. The method of claim 1, further comprising transmitting the set of stimulation parameters for reception by the implantable stimulation device for delivery of electrical stimulation to a patient.
 3. The method of claim 1, wherein a default weighting is assigned to each spatial region absent user selection of the weighting for that spatial region.
 4. The method of claim 1, wherein the stimulation target is a center of stimulation or a virtual electrode.
 5. The method of claim 4, wherein receiving a stimulation target comprises receiving, by the computer processor, a drawing of the virtual electrode on a representation of the lead.
 6. The method of claim 1, wherein steps of receiving a stimulation target and determining a target stimulation field together comprise receiving, by the computer processor, a user-defined target stimulation field.
 7. The method of claim 6, wherein receiving a user-defined target stimulation field comprises receiving, by the computer processor, a drawing of the user-defined target stimulation field relative to a representation of the lead.
 8. The method of claim 1, further comprising receiving, by the computer processor, a user-definition of at least one of the spatial regions relative to a representation of the implanted lead.
 9. The method of claim 1, wherein determining, using the weightings for the plurality of spatial regions, a set of stimulation parameters comprises minimizing, by the computer processor, a weighted error between the generated stimulation field and the target stimulation field using the weightings for the spatial regions.
 10. The method of claim 9, further comprising receiving, by the computer processor, a selection of a model for determining the weighted error.
 11. The method of claim 1, further comprising displaying, on a display coupled to the computer processor, the target stimulation field and the generated stimulation field.
 12. The method of claim 1, further comprising receiving, by the computer processor, a setting of at least one of the electrodes to a zero stimulation amplitude prior to the determining of the set of stimulation parameters and requiring, during the determination of the set of stimulation parameters, that the at least one of the electrodes set to the zero stimulation amplitude remains at the zero stimulation amplitude.
 13. The method of claim 12, further comprising upon receiving the setting of the at least one of the electrodes to a zero amplitude, presenting, by the computer processor on a display, a menu of user-selectable reasons for the setting.
 14. The method of claim 1, further comprising receiving, by the computer processor, a setting of at least one of the electrodes to a fixed stimulation amplitude prior to the determining of the set of stimulation parameters and requiring, during the determination of the set of stimulation parameters, that the at least one of the electrodes set to the fixed stimulation amplitude remains at the fixed stimulation amplitude.
 15. The method of claim 1, wherein the weighting for user selection is a qualitative, non-numerical description of the weighting.
 16. The method of claim 1, wherein the spatial regions are pre-defined.
 17. The method of claim 1, wherein the spatial regions comprise at least one close region, at least one medial region, and at least one far region, wherein the at least one close region is defined nearer the lead than the at least one medial region which, in turn, is defined nearer the lead than the at least one far region.
 18. A non-transitory computer-readable medium having processor-executable instructions for determining a set of stimulation parameters, the processor-executable instructions when installed onto a device enable the device to perform actions, including: receive a stimulation target; determine a target stimulation field based on the stimulation target; receive a selection of a weighting for at least one or a plurality of spatial regions defined relative to a lead comprising a plurality of electrodes, wherein a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determine, using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.
 19. A system for determining a set of stimulation parameters, the system comprising: a display; and a computer processor coupled to the display and configured and arranged to perform the following actions: receive a stimulation target; determine a target stimulation field based on the stimulation target; receive a weighting for a plurality of spatial regions defined relative to a lead comprising a plurality of electrodes, wherein a weighting for at least one of the spatial regions is different from a weighting for another one of the spatial regions; and determine, using the weightings for the plurality of spatial regions, a set of stimulation parameters to produce a generated stimulation field that approximates the target stimulation field.
 20. The system of claim 19, further comprising an implantable lead and an implantable control module coupleable to the lead and configured and arranged to receive the set of stimulation parameters from the computer processor and to deliver electrical stimulation to a patient using the lead according to the set of stimulation parameters. 